The effect of radiation dose to the brain on early self-reported cognitive function in brain and head-and-neck cancer patients

Purpose: Assess cognitive changes after radiotherapy (RT) in brain and head-and-neck (HN) cancer patients using patient-reported outcome measures (PROMs) and evaluate a dose–effect relationship for brain structures. Materials and methods: Primary brain and HN cancer patients treated with RT between 2012–2021 were included. Patient characteristics, clinical parameters, and PROMs at baseline and 1-year follow-up were collected. Cognitive functioning (CF) from the EORTC QLQ-C30, communication deficit (CD) from the QLQ-BN20, and one cognition-related questions from the EQ6D questionnaire were used, the latter two only for brain patients. Missing data were imputed and the four-point scale scores were transformed to a 100-point scale. Change in scores from baseline to 1-year were categorized into improvement/constant or deterioration. Organs-at-risk (OARs) were contoured either clinically or retrospectively using autocontouring and dose to the OARs were calculated. Results: A total of 110 brain and 356 HN cancer patients were included. Median age was 56 (brain) and 67.5 (HN) years. Baseline and 1-year CF was significantly lower for brain patients (p < 0.001). Univariate analysis for ΔCF showed that age at start RT ≤ 65 years, receiving chemotherapy, higher CF Baseline score, brain mean dose > 3 Gy, and multiple dose levels to left and right hippocampus were statistically associated with cognitive deterioration. Multivariate analysis for ΔCF identified age at RT ≤ 65 years, higher CF Baseline score, and brain mean dose > 3 Gy as significant predictors. Conclusion: This study identified risk factors for subjective cognitive decline and suggests that patients’ self-perceived cognitive deterioration may be related to age, CF baseline score and brain radiation dose above 3 Gy.